https://xfs.org/api.php?action=feedcontributions&feedformat=atom&user=Vegasseoxfs.org - User contributions [en]2026-04-21T11:46:10ZUser contributionsMediaWiki 1.42.3https://xfs.org/index.php?title=FITRIM/discard&diff=2433FITRIM/discard2012-03-17T03:14:13Z<p>Vegasseo: /* Batch Mode */</p>
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<div>== Purpose ==<br />
<br />
FITRIM is a mounted filesystem feature to discard (or "[http://en.wikipedia.org/wiki/TRIM trim]") blocks which are not in use by the filesystem. This is useful for solid-state drives (SSDs) and thinly-provisioned storage.<br />
<br />
== Requirements ==<br />
<br />
#The block device underneath the filesystem must support the FITRIM operation.<br />
#The kernel must include TRIM support and XFS must include FITRIM support (this has been true for Linux since v2.6.38, Jan 18 2011)<br />
#Realtime discard mode requires a more recent v3.0 kernel<br />
<br />
This can be verified by viewing /sys/block/<dev>/queue/discard_max_bytes -- If the value is zero then your device doesn't support discard<br />
operations.<br />
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== Modes of Operation ==<br />
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* Realtime discard -- As files are removed, the filesystem issues discard requests automatically<br />
* Batch Mode -- A user procedure that trims all or portions of the filesystem<br />
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=== Realtime discard ===<br />
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This mode issues discard requests automatically as files are removed from the filesystem. No other command or process is required.<br />
<br />
There can be a severe performance penalty for enabling realtime discard. (4)<br />
<br />
Realtime discard is selected by adding the filesystem option <code>discard</code> while mounting.<br />
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This can be done by the following examples:<br />
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# placing <code>discard</code> in your /etc/fstab for the filesystem: <code>/dev/sda1 /mountpoint xfs defaults,discard 0 1</code><br />
# mount options: <code>mount -o discard /dev/sda1 /mountpoint</code><br />
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=== Batch Mode ===<br />
<br />
This mode requires user intervention. This intervention is in the form of the command <code>fstrim</code>. It has been included in [http://en.wikipedia.org/wiki/Util-linux util-linux-ng] [http://www.bobsseo.com since] about Nov 26, 2010.<br />
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Usage example:<br />
<code>fstrim /mountpoint</code><br />
<br />
<br />
----<br />
<br />
== References ==<br />
# FITRIM description - Lukas Czerner <lczerner at redhat.com> http://patchwork.xfs.org/patch/1490/<br />
# Block requirements - Dave Chinner <david at fromorbit.com> http://oss.sgi.com/pipermail/xfs/2011-October/053379.html<br />
# util-linux-ng addition - Karel Zak <kzak@xxxxxxxxxx> http://www.spinics.net/lists/util-linux-ng/msg03646.<br />
# Online TRIM/discard performance impact - http://oss.sgi.com/pipermail/xfs/2011-November/053841.html</div>Vegasseo